Art of refining



Patented Get. 3i, 1939 srsgrss e-ArNr ore-lea v 2,178,078 7 am or no Edward John Martin, East 0hlcago,lnd.,.or to Sinclair Refining Company, How York, N. 1,,

a corporation oi Maine Application June 19,1985, erlal No. 27,34?

No Drawing.s

it claims. (on. res-1s) "I'he invention relates, more particularly, to

improvements inv extraction refining operations in which' the oil is treated with refining solvents, such as nitrobenzene, phenol and beta beta dich-- lor ethyl ether, to improvements in dewaxing operations in which the separation or wax is effected in the presence of a benzene, such as benzene'oi' toluene, and to improvements in refining operations combining such extraction and dewaxing operations.

The use of selective solvents, such as those mentioned, toseparate rafiinates from constituents undesired as components of the particular product in extraction operations and the use of benzenes to assist in the separation of ramnates from wax in dewaxing operations has hitherto been proposed. In such extraction operations as previously practiced, however, the optimum extraction temperatures are usually relatively low, so low as to involve mechanical diiiiculties as applied to waxy stocks for'example. Also, refining solvents of the type mentioned tend to separate from the ramnate in solution with the undesired constituents whereas the benzenes tend to separate from the wax in solution with the ramnate, necessitating stripping of the refining solvent from the raflinate from the extraction operation,

with which a minor proportion of the solvent is such extraction and dewaxing operations to be combined in a particularly advantageous man-' ner.

In the improved extraction operation of my invention, the optimum temperature is increased by the addition of ethylene glycol monomethyl ether to refining solvents tending to separate from the ramnate. in solution with the undesired constituents. The oil component oi the rate My invention further .in-

is less soluble in the mixture oi refining solvent and ethylene glycol monomethyl etherthan in the refining solvent alone thus permitting increase of the temperature at which the extraction is eflected without increase in loss oi such oil component in solution with the extract. The ex-' traction efliciency of the refining solvent is improved at higher temperatures and improvemeat-in the extraction operation is thus attained. Also, as applied to waxy stocks for example. it thus becomes possible to carry out the extracting operation at optimum temperature while avoiding mechanical difliculties due to the presence of waxj In this aspect, the invention makes the extraction operation applicable to stocks otherwise impos- '16 sible to, treat by the operation, Addition of ethyl-- 1 ene glycol monomethyl ether to the refining solvent decreases its solvent capacity for constituents undesired as components of the refined product but this is oii'set by an increase in this sol-- vent capacity and in extraction eiiiciency at higher extraction temperatures, and any remaining net efi'ective decrease in solvent capacity can be made up by increasing the proportion in which the refining solvent is used.

The solvent mixture used in dewaxing operations, in accordance with my invention includes one or more benzenes and ethylene glycol monomethyl ether, and may include, with advantage, a. small proportion of a refining solvent of the type mentioned. a proportion corresponding lor. example to that in which such solvents remain associated with rafiinates in extraction operations in which they are used. In the dewaxing solvent mixtures of my invention, the presence in such proportions of such refining solvents improves the dewaxing operation. The dewaxing solvent mixtures of my invention are particularly advantageous as applied to more viscous stocks.

In the combined extraction and dewamng operation of my invention, the extraction operation and the dewaxing operation are each effected with the aid of solvents, such as those mentioned, and ethylene glycol monomethyl ether is added to the dewamng. solvent mixture. Any necessity for stripping the refining solvent from the rafilnate from the extraction operation before it is subjected to the dewaxing operation can thus be avoided, since the proportions of the refining solvent usually retained in association with this ramnate improve the dewaxing operation when the solvent mixture of my invention is used in the dewaxing operation, and important economles with respect to apparatus required as well as in the combinedoperation itself can thus be secured. Ethylene glycol monomethyl ether is, with advantage, also used with the refining solvent in the combined extraction and dewaxing operation of my invention.

In one way of carrying out the combined exarraove J traction and dewaxing refining operation of my invention, for example, the stock from which the refined lubricating oil is to be produced is subjected to extraction with a refining solvent or, with advantage, with a solvent mixture including a refining solvent and ethylene glycol monomethyl ether. In the latter case, the ratio of ethylene glycol monomethyl ether to the refining solvent in the solvent mixture is adjusted, m for example, to effect optimum extraction at the chosen extraction temperature. The extraction temperature is chosen with respect to the particular stock, for example, to facilitate the hen dling of the stool; in the extraction operation 5 and to secure satisfactory extraction eficiency. With waxy stocks, for example, a temperature high enough to insure fluidity of the stock notwithstanding the presence otthe wax is used. The extract is separated from the raillnate, the 29 bulk of the solvent. mixture separating with the extract but a minor proportion of the constituents of the solvent mixture remaining in association with the raffinate. The raffinate with associated constituents of the refining solvent is subjected directly to the dewaxing operation, that is prior to any stripping of the associated solvent constituents from the ramnate. The dewaxing operation is carried out as in conventional practice except that the separation of my wax from the ramnate is efifected in the presence of a solvent mixture including, for example, benzene or toluene or a mixture oi the two, the re-' fining solvent constituents carried over with the rafiinate from the extraction operation, and

g5 ethylene glycol monomethylether. The dewaxing solvent including ethylene glycol monomethyl ether is added to the rafinate from the extraction operation prior to chilling preceding the separa tion of wax. If the refining solvent used in the g extraction operation does not include ethylene glycol monomethyl ether, the full proportion of this compound to be used in the dewaxing operation is added with the dewaxing solvent mixture,,but if this compound is used in the refining w solvent due allowance is made for that proportion carried over with therafiinate from the extraction operation. Solvent constituents are stripped by distillation from the ramnate from the dewaxing operation following the extraction operation,

50 from the wax separated in the dewaxing operation and from the extract separated in the extraction operation. The distillates from these three stripping operations are combined and redistilled to separate and recover for re-use the 55 severalsolvent constituents. For example, in an operation using a mixture of nitrobenzene and ethylene glycol monomethyl ether as a refining solvent and a mixture of benzene or toluene or both and ethylene glycol monomethyl ether as 60 the dewaxing solvent mixture, the combined distillates can be separated in a single still equipped to separate a. light fraction and an intermediate fraction as well as a residual fraction or in two stills in series. The combined distillates are 65 separated, for example, into a light fraction comprising the benzene or toluene or both together with any water condensed from steam used in the stripping distillations, an intermediate frac- .tion consisting of the ethylene glycol monomethyl 7 ether and a residual fraction consisting of the nitrobenzene, water being separated by gravity from the hydrocarbon component of the light fraction. The rafllnate from the dewaxing operation following the extraction operation, after 75 stripping of associated sol-vent constituents, is

traction operation and the dewaxing operation of my invention.

Example I An undewaxed Mid-continent neutral oil stocir having a viscosity of 201 seconds at 100 F. Saybolt Universal, a pour test of 80 F. and a Conradson carbon of 0.019 was subjected to extractionat 100 F. with 1.10% (by volume on the charge of raw stock) of a refining solvent mixture consisting of 6 parts nitrohenzene and 5 2( parts ethylene glycol monomethyl ether to produce a 71.4% yield of a waxy rafinate having a viscosity of 155. seconds at 100 and its seconds at 210 F Saylcolt Universal, a pour test of 90 F. and a Conradson carbon of 0.01%. The 25 extraction was carried out in six stages with countercurrent contact in each stage. Th6 settling time for separation of raiiinate and extract in each stage was ten minutes. The solvent constituents remaining associated with the rafilnate amounted to 15.5% (by volume on the charge of raw stock). The raffinate from the extraction including associated solvent constituents, was mixed with 300% (by volume on the charge of rafiinate) of, a dewaxing solvent mixture consisting of '7 parts benzene and 3 parts ethylene glycol monomethyl ether and chilled to 10 F. Precipitated wax was filtered from the oil-solvent mixture to produce a yield of 86.8% (by volume on the rafllnate from the extraction operation, 40 62.0% on the charge of raw stock) oL-a raflinate having a viscosity of 190.6 seconds at 100 F. and 45.4 seconds at210 F. Saybolt Universal, a pour test of 5 F. and a Conradson carbon of 0.014. The viscosity index of the raiiinate from the dewaxing operation following the extraction operation was 90.9. The viscosities, pour tests and Conradson carbon contents given with respect to the raihnate from the extraction operation and the raflinate from the dewaxing operation following the extraction operation are valuesdetermined from samples after separation of asso-' elated solvent constituents. After being stripped 01' solvent constituents, the rafllnate from the dewaxing operation was contacted with 10% (by weight on the ramnate) of fullers earth (Olmstead) at 180 F. to produce a finished lubricating oil having'a viscosity of 190.4 seconds at 100 F. and 45.4 seconds at 210 F. Saybolt Universal,

8. pour test of 0 F., a Conradson carbon 01' 0.013, a 2+ color and a viscosity index of 91.

Example II A Mid-Continent overhead long residuum having a viscosity of 138 seconds at 210 F. Saybolt Universal, a pour test of F. and a Conradson carbon of 2.962 was subjected to extraction at F. with (by volume on the charge of raw stock) of a refining solvent mixture consisting of 4 parts nitrobenzene and 3 parts ethyl- 70 ene glycol monomethyl ether to produce a 53.0% yield of a waxy raflinate having a. viscosity of 96.2 seconds at 210 F. Saybolt Universal, 9. pour test of 100 F. and a Conradson carbon of 0.471. The extraction was carried out in six stages with 75 arraore countercurr ent contact in each stage. The settling time for separation of railinate. and extract in each stage was 30 minutes. The solvent constituents remaining associated with the ramnate amounted to 20.2% (by volume on he charge of raw stock) comprising 17.3% of nltrobenzene and 2.9% of ethylene glycol monomethyl ether. The ramnate from the extraction, including the associated solvent constituents, was mixed with 300% (by volume on the charge of ramnate) of a dewaxing solventmixture consisting of 55 parts benzene, 22 parts toluene and 23 parts ethylene glycol monomethyl ether and. chilled to -20 F. Precipitated wax was filtered from the oil-solvent mixture to produce a yield of 79.4% (by volume on the rafiinate from the extraction operation) of a ramnate having a viscosity of 106.9 seconds at 210 F. Saybolt Universal, 8. pour test of +5 F. and a Conradson carbon of 0.535. The viscosity index of the ramnate from the dewaxing operation iollowing'the extraction operation was 87.8. The viscosities, pour tests and Conradson carbon contents given with respect to the rafiinate from the extraction operation and the rafiinate from the dewaxing operation following the extraction operation are values determined from samples after separation of associated solvent constituents. After being stripped of solvent constituents the rafilnate from the dewaxing operation was contacted with 10% (by weight on the ramnate) of acid-treated clay (Terrana) at 450 F. to produce a finished lubricating oil having a viscosity of 105.3 seconds at 210 F. and 1,4179 seconds at 100 F. Saybolt Universal, a pour test of +5 R, a Conradson completely miscible with the refining solvent,

having little if any solvency for oil and having a selective solvency, even thougl'. very slight, for constituents undesired as compo..ents of the ram= nate, are as a class useful as such modifiers and when I use the term fmodifier herein I mean agents having these properties. The ethylene glycol ethers, however, appear to be advantageous modifiers and I have found ethylene glycol monomethyl ether .to be a particularly advantageous modifier. In the combined operation of my invention, one modifier may be used in the refining operation and another, in addition to any part of the first retained in association with the rafllnate from the refining operation, may be used in the dewaxing operation.

When I refer to refining solvents herein, I mean solvents the bulls of which separates from the rafilnate in solution with the constituents undesired as components of the rafiinate. When I refer to dewaxing solvent mixtures" herein, I mean solvent mixtures the bulk of which separates from the wax in solution with the ramnate. When I use the term a benzene herein, I mean benzene, toluene or any homologue having the same solvent characteristics with respect to wax and oil.

I claim:

1. In the dewaxing of lubricating oils, the improvement which comprises separating wax from the stock in the presence of a solvent mixture including a benzene and ethylene glycol monomethyl ether.

2. A ,dewaxing solvent mixture for dewaxing lubricating oils comprising a benzene and ethylene glycol monomethyl ether.

3. In the refining of lubricating oils, the improvement which comprises extracting the stool: with nitrobenzene, separating the extract from the ramnate, and separating wax from this remnnate in the presence of a solvent mixture including a benzene. ethylene glycol monomethyl ether and nitrobenzene.

4. In the refining of lubricating oils, the improvement which comprises extracting the stock with a refining solvent, separating the extract from the raffinate, and separating wax from this rafiinate in the presence of a solvent mixture including a benzene, an ethylene glycol ether and the refining solvent.

5. In the refining of lubricating oils, the im' provement which comprises extracting the stock with a refining solvent, separating the extract from the raifinate and separating wax from this ramnate in the presence of a solvent mixture including a benzene, a modifier of the 01% described and the refining solvent.

6. In the refining of lubricating oils, the improvement which comprises extracting the stock with a solvent mixture inciudingnitrobenzene and ethylene glycol monomethyl ether, separating the extract from the raffinate, and separating wax from this rafiinate in the presence of a solvent mixture including a benzene, etmlene glycol monomethyl ether and nitrobenzene.

'7. In the refining of lubricating oils, the improvement which comprises extracting the steels with a solvent mixture including a refining solvent and an ethylene glycol ether, separating the extract from the rafilnate, and separating wax from. this rafilnate in the presence of a solvent mixture including a benzene, an ethylene glycol ether and the refining solvent.

8. In the refining of lubricating oils, the improvement which comprises extracting the stock with a solvent mixture including a refining solvent and a modifier of the class described, separating the extract from the rafllnate and separating wax from this raifinate in the presence of a solvent mixture including a benzene, the modifier and the refining solvent.

- 9. In the refining of lubricating oils, the im-.

provement which comprises extracting the stock with a solvent mixture including a refining solvent and a modifier of the class described, sepaprovement which comprises extracting the stock with a. solvent mixture including a refining solvent and a modifier of the class described, separating the extract from the rafilnate and separating wax from this raflinate in the presence or a solvent mixture including a benzene, that modifier and another modifier of the class described, and the refining solvent.

' EDWARD JOHN MARTIN. 

